Controlling means for electric heaters



T. KL'c'rrzu CONTROLLING MEANS FOR ELECTRIC HEATERS Oct. 21 1924.

Filed Sept. 13

Patented Oct. 21, 1924.

UNITED STATES PATENQT OFFICE.

THEODOR KLTZLI, OF THOU'NE, SWITZERLAND.

CONTROLLING means son ELECTRIC nm'rnns.

Application filed September 13, 1920. Serial No. 410,035.

an improved safety device for preventing the same from becoming overheated.

According to my invention, an electric iron or the like is rovided with'a switch having a member that tends automatically to open the circuit, and isheld in its circuit-closing position by a locking member which is situated in operative relation to an expansion member to be mounted on the iron or the like, so that when the expansion member expands a predetermined amount owing to a rise in temperature of the iron or the like the said member moves out of its circuit-closing position and opens the circuit. v

The invention consists in the construction, arrangement and combination of parts de scribed hereinafter and pointed out in the 7 claims.

One illustrative embodiment of the invention and several modifications thereof are represented b way of example in the accompanying rawing, wherein:

Figure 1 is a cross-sectional elevation of one form of safety device according to the invention, and

Figure 2 is a vertical lon itudinal section taken on the line IL-H in igure 1;

Figure 3 is a view corresponding to Figure 1 showing a second form, and

Figure 4 1s a side elevation of an iron comprising a modified detail;

Fi ure 5 is a vertical sectional elevation showing a third form,

Fi ure 6 is a section taken on the line vr vr in Figure 5, and

Figure 7 is a bottom plan view thereof.

In the construction shown in Figures 1 and 2, the body 1 of an electric iron carries at its rear end two contact pins 2 which are received h the two contact sockets 3 and 4;; provided in the plug 5. The socket 3 is connected by a .wire 6 and a terminal 7 with a wire 8 of a lug flexible-cord connected to the latter, whi st the other wire 9 of the same cord can be brought into electrical connection the socket 4% by two laterally-bent contact-springs 12 and 13 mounted respectively on arms 10 and 11 projecting laterally away from the body of the plug 5.

The leaf spring 13 ten to move away from the contact spring 12. to break the circuit; in order to close the circuit it must therefore be pressed against the spring 12. For this purpose there .is provided a slide 15 having a lateral pin 14 of insulatin material. This slide is movable up and down, is guided by two ins 16 mounted on a sheetinetal casing 1.7 ietachably attached to the plug 5, and is normally held in its upper position by a spiral spring 18. By pressing a knob 19 on the top of the slide 15 the latter can be moved against the action of the spring 18 into its lower position, wherein it is held by a catch 20 arranged to engage in a recess 21 in the slide.

The catch 20 has below its pivot 22 a short arm 23 which carries a micrometer screw 25 arranged to coact with the free end of a rodor bar 24 of angular section having its other end firmly connected with the body 1 of the IIOIX.

This bar 24 consists of a metal, for example zinc, having a considerably greater coefficient of expansion than that of the.

body of the iron, and lies lengthwise freely on the latter, being thus in heat-conducting relationship therewith. If the iron has attained a certain temperature which, if it lasted a long time, might lead to the destruction of, for example, the heating resistance,

then in consequence of the expansion in length of the bar 24 the catch 20 will be disengaged by the bar from the recess 21 in the slide 15. This slide will at once fly upwards, its pin 1 will consequently release the contact spring 13 which will immediately moveaway from the contact spring 12 and thereby break the circuit. This interruption will be permanent, that is to say the current will not be switched on automatically when the temperature of the iron falls again; the circuit must be closed manually by pressing down the slide 15. Also, the circuit cannot be kept closed by the device belorethe bar 24 has contracted owing to the iron cooling.

in the example described above with reference to Figures 1 and 2 the switch (15) together with the plug (5) is detachably mounted on the iron. lternatively, the entire device can be fixedly mounted on the iron .and so constructed that an ordinary plug can be connected to it. For this purpose, as shown in Figure 3, the socket 3 is tubular and has its upper end arranged to receive the pin of a plug; above the socket 4 is arranged a sleeve 125 for receiving the other pin of the plug, which sleeve 125 carries the arm 11. The lower part of the sleeve 3' and the socket 4 are pushed onto pins on the iron and can be securely fixed thereto each by a set-screw, for example, not shown in the drawing.

In the examples described above the rod 24 is attached directly to the iron. The expansion in length of the latter due to its being heated acts counter to that of the rod 24. In order to obviate this drawback in the construction according to Figure 4 the rod 94 is fixed not directly to the body of the iron itself, but to a rod 27 mounted on the casing of the switch, a layer of heat insulating material (not essentially shown) being provided between the two rods. The

expansion of the iron can therefore in no' way materially impair the effect of the expansion of the. rod 24, because. the rod 27 will experience a scarcely appreciable expansion due solely to heat radiated by the iron.

In the embodiments illustrated in Figures 1 to 4 the expansion member is in the form of a relativel long rod that has to be arranged outsi e the casing of the switch on the iron. This gives, to the device a clumsy appearance, and necessitates the switch and the rod being suitably arranged on the iron. A construction in which the expansion member is accommodated within the switch casing would therefore be preferable in, practice. In the embodiment according to Figures 5 to 7' this end is attained by making the expansion member of at least two rods arranged side by side which act longitudinally one on the other at one end by means of an intermediate member.

Referring to Figures 5 to 7, the plug 35 of insulating material is provided with two contact sockets 33 and 34, at the usual distance apart whereof the latter has on a laterally projecting lug 40 an upwardly extending contact leaf spring 43. A contact lug 41 of a connection member 39 arranged above the socket 34 projects out of the plug 35 adjacent'to, but spaced apart from the upper end of this spring 43. The wires of a flexible cord from a plug can be led to the contact socket 33 and to the member 39 by way of a hole 38 that is made in the top of the plug 35 and has two branches at. its lower end. In order to close the switch 41, 43 or the circuit terminating thereat, a cut-out member, in the form of a metal ring 44 can be inserted from above between the two members 41, 43 by pressing downwards against the action of the spring 48 .a sliding rod 45 that is guided to move up and down at a side wall of the casing 47 and. carries the ring 44, but is insulated therefrom. When the rod 45 is in its lowest position it is held therein by a springcontrolled catch 50 that takes into a recess 51 in the rod. This catch 50 has below its pivot 52- a short arm 53 which extends into operative relation with a rod 54 of material, for example zinc, having a'high coefiicient of expansion. This rod 54 is guided to slide longitudinally on the bottom of the switch casing 47 in a recess in the plug 35 close to a second rod 54' that consists of the same material as the rod 54. A sickle-shaped rolling lever 57 resting freely in the recess 49 on the bottom of the casing 47 is provided at the ends of the rods 54, 54' remote from the catch 50 and serves to impart to therod 54 the longitudinal expansion of the rod 54 due to its rise in temperature. In order that the heat can be transmitted directly from an iron device to the rods 54, 54

which conjointly constitute the expansion member, the bottom of the casing 47 has in it a slot 47',

through which lugs or projections 56 on the bottom faces of the rods can extend and bear directly upon the iron when the plug 35 is pushed home on the pins provided for it on the iron. is screwed into the rod 54 of the casing 47 45, which screw serves to predetermine at what temperature the electric current isto be cut off or theswitch is to be opened. When the expansion member hasexpanded an amount corresponding to the maximum admissible temperature, the catch 50 will release the thrust rod 45 which will at once fly into its upper end position. The contact ring 44 thereby, breaks contact with the spring 43 and consequently breaks the circuit. When the iron or the expansion member cools the circuit is not closed automatically, but its closure must be efiected manually by depressing the rod 45.

By subdividing the expansion member 54, 54 into two ormore parts it is possible to accommodate it in a small space such as inside the casing of the switch. The safet device "in the form last described with reference to Figures 5 to 7 can consequently be put on the market as a unitary structure, and can be readily connected to a flexible cord of a plug in the ordinary manner. Also the appearance of an iron s not impaired by the device.

The described safety device can be applied to most existing electric irons and also, for example, to electric cooking utensils, and has the advantage that its employment prevents not only overheating of the iron or the like, but also consequential scorching of linen in the side wall A set-screw 55 provided with the safety that carries the thrust rodand other combustible articles in 139 contact with the hot iron or the like, and may effect a material saving of electric current.

I claim:

1. A thermostatic switch comprising a detachable casing, electric contacts therein, an expansion member, a movable member for opening and closing the said contacts, a means tendin to move the said movable member to its inoperative contact-opening expanded by ,heat a predetermined amount, the said catch 'is automatically withdrawn so as vto release the said movable member from its operative contact-closing position.

2. A thermostatic switch as specified in claim 1, in which-the said expansion member so disposed relative to the said expansion member that on the latter being consists in a metal rod having a high coeflicient of expansion, means being provided projecting from the bottom of the said casing egg arranged to transmit heat to the said A 3. A thermostatic switch as specified in claim 1, in which the said expansion member consists in a metal rod havin a high 00- eflicient of expansion, means being provided projecting from the bottom of the said casing and arranged to transmit heat to the said rod, the latter consisting of two adjacent parts and a sickle-shaped rolling lever at the ends of the said parts for imparting the expanding movement of the one part to the other. 7 v

In testimony whereof, I afiix my signature in the presence of two witnesses.

THEODOR KLOTZLI. v Witnesses:

J. ALLEMANN, R. Hnmeax'rm. 

